1. Field of the Invention
This invention pertains to padlocks. More particularly, this invention pertains to the lock cylinder of a rekeyable padlock.
2. Description of the Prior Art
Padlocks are commonly used to secure belongings in structures such as sheds, trunks, lock boxes, and the like. One type of padlock is a combination padlock in which a combination (i.e., a unique code typically represented by numbers) is used to unlock the padlock. However, several problems may occur with combination padlocks. The user may forget the combination, and, therefore, be unable to open the padlock. The user may write down the combination, which could compromise the security of the lock. In addition, if the lock is not used often, the user may forget where the written combination was stored.
A keyable padlock is another common type of padlock. Keyable padlocks are advantageous over combination padlocks because keyable padlocks do not require memorization of a combination. Rather, a key is used to unlock the padlock. However, the user of a keyable padlock must either store the padlock key in a place that is easy to remember, or carry the padlock key with other commonly used keys. Storing the padlock key increases the risk that the user will forget where the padlock key is stored or that the padlock key will not be found again. Carrying the padlock key with other commonly used keys, however, increases the bulk of the user""s key chain and can be a source of irritation if the user has multiple padlock keys for multiple padlocks.
Keyable padlocks are known in the art, such as the ones described in U.S. Pat. Nos. 5,363,678 and 5,377,511 issued to Meckbach on Nov. 15, 1994 and Jan. 3, 1995, respectively, and hereby incorporated by reference in their entirety. Keyable padlocks such as these are not typically sold to end users, but rather are first xe2x80x9ckeyedxe2x80x9d by a locksmith and then sold to users. The padlocks are provided to a locksmith with a zero-bitted key, meaning that the key has two long, generally parallel edges with no cuts. The locksmith removes a cylinder of the padlock body and then inserts the zero-bitted key into a rotatable core of the cylinder. A stop pin limits rotation of the rotatable core of the cylinder. The stop pin must be removed from the cylinder in order to complete the rotation of the core to align the key opening with a longitudinal row of pin openings in an outer casing of the cylinder. Generally, tweezers, pliers, or another similar tool can be used to remove the stop pin from the cylinder.
The locksmith determines a pin sequence for each padlock. Specifically the locksmith selects a predetermined number of pins to insert in the pin openings of the cylinder, with each pin having a specific length and with the pins ordered in a particular sequence. Generally, a padlock cylinder accommodates between 3 and 7 pins. It is desirable for the pins to be small in length and width because a padlock""s security increases as the number of pins used in the pin sequence increases. Thus, a padlock accommodating a seven-pin pin sequence has a higher level of security than a padlock accommodating only a three-pin pin sequence.
It is also desirable to have multiple pin lengths from which to choose, because this also enhances the security of the padlock. Typically, the pins used in a pin sequence are selected from a group of pins having a variety of pin lengths. For example Schlage(copyright) padlocks accommodate ten different pin lengths, although generally the zero-bit is not used. Therefore, pins are selected for the pin sequence from the remaining nine of the ten pin lengths. In another example, Kwikset(copyright) padlocks accommodate six different pin lengths.
As the pins become smaller and as the number of pins used and the number of variations of pin lengths increases, however, the more difficult it becomes to differentiate pins having the different pin lengths. In some prior art padlocks, such as the Schlage(copyright) padlocks, the variation between successive pin lengths is not more than 0.015 inches. In other prior art padlocks, such as Kwikset(copyright) padlocks, the pin lengths will vary between 0.021 and 0.027 inches between successive pin lengths. With such small variations in pin length, special tools are needed to differentiate between the lengths of the pins. Other systems, such as that illustrated in U.S. patent Ser. No. 09/561,157, filed Apr. 28, 2000, hereby incorporated by reference in its entirety, uses color coding to differentiate between the lengths of pins.
After the pin sequence is selected and before inserting the pins through the pin holes, the zero-bitted key is removed from the key opening and one edge of the key is cut such that the number, size, and order of cuts in the edge of the key correspond to the number, length, and order of the pins of the selected pin sequence. The cut key is then inserted into the key opening and the selected pins are inserted into the pin openings in the specified order of the pin sequence. After all of the pins are inserted, a shear line is formed and the key is rotated. Once the stop pin opening is accessible, the stop pin must be inserted back into the stop pin opening and the key is rotated until the pins are aligned with bottom pins and springs that prevent rotation of the cylinder core without the matching key.
The relatively small size of the pins, in addition to the small differences in length of the pins, make the process of selecting the pin lengths, arranging the pins in the selected sequence, and cutting a key to correspond to the selected pin lengths and sequence, a painstaking task. The placement of a pin that is even one size too short into one of the pin openings could result in a cylinder core that cannot be turned with the cut key. In such a situation, the cut key would be able to turn the cylinder core until the pins were aligned with the springs and bottom pins that prevent rotation of the cylinder core without the matching key. Once the pins in the cylinder were aligned with the springs and bottom pins, however, the key would not be able to turn the cylinder core to unlock the padlock, nor would it be able to turn the cylinder core to replace the short pin to match its corresponding key cut. Because of the high level of accuracy needed to ensure that the lengths and sequence of the pins match the depths and sequence of the cuts in the key, padlocks of this type are not typically sold directly to consumers. In addition, most consumers have to go to a hardware store or the like in order to use key cutting machines. Therefore, these types of padlocks are not sold to consumers until after a locksmith has keyed the lock and ensured that it is operational with the provided key.
What is needed is a simplified method and padlock that enables a consumer to key the padlock to a particular key that is already cut and that is selected by the user. For example, if a consumer purchases one or more padlocks, it is desirable that the consumer be able to key each of the padlocks to operate with a particular key, such as the consumer""s house key. Thus, the consumer would not have to maintain separate and additional keys for each individual padlock.
The present invention provides a solution to these and other problems and offers other advantages over the prior art, as will be understood with reference to the summary, the detailed description and the drawings.
According to a preferred embodiment of the present invention, a rekeyable padlock is provided with a lock cylinder formed within. The lock cylinder includes a cylindrical core formed to receive a key and an outer casing formed around the core. A viewing opening is formed within the casing wall, the viewing opening allowing access to pin openings formed within the core to receive selected pins. The viewing opening is shaped such that it provides a viewing area larger than the pin openings, thereby allowing greater visibility when the pins are placed within the pin openings. The advantages of this viewing opening include greater ease in placing the pins into the pin openings and easier detection when a selected pin is the wrong length and does not sit flush within the lock cylinder core.